Many steel components of machines and other devices are machined from bar or rod forms of steel alloys. However, the machining process for making such parts, particularly fasteners, results in significant amounts of wasted material. Therefore, parts that were traditionally machined are now being engineered to be fabricated by cold forming techniques such as cold heading.
The shift to the cold forming of steel parts presents a significant problem when in addition to cold formability, corrosion resistance and high strength are required in the steel parts. Hitherto, when high strength and corrosion resistance are needed in a steel part, precipitation hardenable stainless steels have been used. However, the known precipitation hardenable stainless steels do not provide adequate cold formability because of their high annealed hardness which is typically greater than about 100 HRB. The known martensitic stainless steels, although providing somewhat better cold formability, leave something to be desired with their corrosion resistance. Austenitic and ferritic stainless steels provide better corrosion resistance than martensitic stainless steels, but do not provide the strength needed for many applications. In addition, some cold-formed parts may also require a small amount of machining to achieve their final shape and dimension. The use of free-machining additives can adversely affect other desired properties in cold-formable steel alloys.
In view of the foregoing comments, a need has arisen for a martensitic stainless steel with a combination of high strength, corrosion resistance, and good cold formability that is better than the known cold formable stainless steels. It would also be desirable to have such a steel that provides good machinability without adversely affecting the cold formability of the alloy.